VLESS Connection Errors: Fixes for Reality Handshake, TLS & Timeout (2026)

VLESS Reality is the most detection-resistant proxy protocol available in 2026, but its advanced security features mean that misconfigurations produce cryptic error messages. This guide covers every common VLESS error, explains exactly what causes it, and provides the precise fix. All solutions are tested on xray-core 25.x with V2rayN 7.x and v2rayNG 1.9.x as of April 2026.

Error: "VLESS Reality Handshake Failed"

What This Error Means

The VLESS Reality handshake is a cryptographic key exchange that happens inside what looks like a normal TLS connection. When this error appears, the client successfully connected to the server on the network level, but the Reality authentication failed. The server rejected the client's credentials.

What Causes It

• Mismatched public key: The client's pbk (public key) does not match the server's private key. This is the most common cause.
• Wrong shortId: The sid (short ID) in the client config is not in the server's shortIds array.
• SNI mismatch: The sni in the client does not match any entry in the server's serverNames array.
• Server not running Reality: The server is configured for regular TLS, not Reality, but the client is trying to use Reality.

How to Fix It

Step 1: On the server, regenerate and verify the key pair:

xray x25519
# Output:
# Private key: MC4CAQAwBQYDK2VuBCIE...  (use this in server config)
# Public key:  MCowBQYDK2VuAyEA...     (give this to client)

Step 2: Verify the server config contains the private key and shortIds:

"realitySettings": {
  "dest": "www.microsoft.com:443",
  "serverNames": ["www.microsoft.com"],
  "privateKey": "YOUR-PRIVATE-KEY-HERE",
  "shortIds": ["abcdef1234", ""]
}

Step 3: Verify the client config uses the matching public key:

vless://uuid@server:443?security=reality&pbk=YOUR-PUBLIC-KEY&sid=abcdef1234&sni=www.microsoft.com&fp=chrome&flow=xtls-rprx-vision#name

Step 4: Ensure the sni matches a serverNames entry exactly (case-sensitive, including www. prefix if present).

Step 5: Restart xray-core after any config change:

sudo systemctl restart xray

Error: "Connection Refused" / "Connection Timeout"

What This Error Means

The client cannot establish a TCP connection to the server at all. The connection either gets actively rejected (connection refused, meaning the server's port is closed) or silently dropped (connection timeout, meaning packets are being blocked by a firewall).

What Causes It

• Firewall blocking port 443: The server's firewall (iptables, ufw, or cloud provider security group) is not allowing incoming connections on the configured port.
• xray-core not running: The xray process crashed or was not started.
• Wrong server IP or port: The client config points to the wrong address.
• ISP/network blocking: The client's network is blocking outbound connections to the server IP.
• Server overloaded: The server has too many connections and is refusing new ones.

How to Fix It

Step 1: Verify xray-core is running on the server:

sudo systemctl status xray
# Should show "active (running)"

# If not running:
sudo systemctl start xray
sudo journalctl -u xray -n 50 --no-pager  # Check for startup errors

Step 2: Verify the port is open and listening:

sudo ss -tlnp | grep 443
# Should show xray listening on 0.0.0.0:443 or [::]:443

Step 3: Check firewall rules:

# UFW:
sudo ufw status
sudo ufw allow 443/tcp

# iptables:
sudo iptables -L INPUT -n | grep 443

# Cloud providers: check security group / firewall rules in the web console

Step 4: Test connectivity from the client side:

# From client machine:
telnet your-server-ip 443
# Or:
curl -v https://your-server-ip:443 --connect-timeout 5

Step 5: If timeout persists, the server IP may be blocked by the client's ISP. Test from a different network (mobile data, different Wi-Fi) to confirm. If the IP is blocked, you need to change the server IP or use a CDN relay.

Error: "TLS: Failed to Verify Certificate"

What This Error Means

The client is trying to verify a TLS certificate during the connection, but verification fails. This error typically occurs when using standard VLESS+TLS (not Reality) or when the client is misconfigured to use TLS verification with a Reality connection.

What Causes It

• Using TLS mode instead of Reality: The client's security is set to tls instead of reality.
• Expired certificate: If using standard VLESS+TLS (not Reality), the Let's Encrypt certificate has expired.
• Wrong SNI: The SNI in the client does not match the certificate's domain.
• Self-signed certificate: The server uses a self-signed cert without the client being configured to accept it.

How to Fix It

For VLESS Reality users: Ensure your client config uses security=reality, not security=tls. Reality does not use traditional TLS certificate verification. The connection string should look like:

vless://uuid@server:443?security=reality&...

Not:

vless://uuid@server:443?security=tls&...

For standard VLESS+TLS users: Renew the certificate:

# If using certbot:
sudo certbot renew
sudo systemctl restart xray

# If using acme.sh:
~/.acme.sh/acme.sh --renew -d your-domain.com --force
sudo systemctl restart xray

Verify certificate status:

echo | openssl s_client -connect your-domain.com:443 -servername your-domain.com 2>/dev/null | openssl x509 -noout -dates

Error: "DNS Leak Detected"

What This Error Means

Your proxy tunnel is working for HTTP/HTTPS traffic, but DNS queries are bypassing the tunnel and going directly to your ISP's DNS servers. This means your ISP (or anyone monitoring your network) can see which domains you are visiting, even though the actual page content is encrypted through the VLESS tunnel.

What Causes It

• DNS not routed through tunnel: The client is only tunneling TCP traffic, not DNS queries.
• System DNS override: The operating system's DNS settings are overriding the tunnel's DNS configuration.
• Split tunneling misconfigured: Only some traffic goes through the proxy, and DNS is in the "direct" category.

How to Fix It

V2rayN (Windows):

1. Go to Settings, then Core: basic settings
2. Set "Domain Strategy" to IPIfNonMatch
3. Under DNS settings, add a DNS server that routes through the proxy:

   {
     "dns": {
       "servers": [
         "8.8.8.8",
         {
           "address": "1.1.1.1",
           "domains": ["geosite:geolocation-!cn"]
         }
       ]
     }
   }

4. Enable "Sniffing" in the inbound settings to capture DNS queries from the TUN interface.

v2rayNG (Android):

1. Tap the server entry, then Edit
2. Scroll to "Domain Strategy" and set to IPIfNonMatch
3. Under "DNS", add 8.8.8.8 or 1.1.1.1
4. Enable "Enable local DNS" and set it to 1.1.1.1
5. Enable "Enable sniffing"

Verify the fix: Visit browserleaks.com/dns while connected. All DNS servers listed should be the ones you configured (8.8.8.8, 1.1.1.1), not your ISP's servers.

Error: "xray-core: Failed to Start"

What This Error Means

The xray-core binary cannot start, usually because of a configuration file error. This error appears in the system journal (server-side) or in the V2rayN log panel (client-side).

What Causes It

• Invalid JSON in config: A missing comma, extra comma, or mismatched bracket in config.json.
• Port already in use: Another process (nginx, Apache, another xray instance) is already listening on port 443.
• Missing binary permissions: The xray binary does not have execute permissions.
• Incompatible config version: Config syntax from an older xray version that is no longer supported.

How to Fix It

Step 1: Check the exact error message:

# Server (systemd):
sudo journalctl -u xray -n 100 --no-pager

# V2rayN: Click the log icon in the bottom-left corner of the main window

Step 2: Validate the JSON config:

# Test config without starting:
xray run -test -c /usr/local/etc/xray/config.json

# Or use jq to check for JSON syntax errors:
jq . /usr/local/etc/xray/config.json > /dev/null

Step 3: Check for port conflicts:

sudo ss -tlnp | grep 443
# If another process is using 443, either stop it or change xray's port

Step 4: Verify binary permissions:

ls -la /usr/local/bin/xray
# Should show -rwxr-xr-x. If not:
sudo chmod +x /usr/local/bin/xray

Common JSON mistakes to check:

• Trailing comma after the last item in an array or object: ["item1", "item2",] (remove the last comma)
• Missing quotes around string values: "port": 443 is correct, "port": "443" is wrong for numeric fields
• Using single quotes instead of double quotes: JSON requires double quotes exclusively

Error: "V2rayN Green Tray Icon but No Connection"

What This Error Means

V2rayN shows a green system tray icon (indicating the local proxy is running), but no traffic actually passes through the proxy. Websites load slowly or not at all, or they load using your real IP instead of the proxy IP.

What Causes It

• System proxy not set: V2rayN started its local SOCKS/HTTP listener, but the operating system is not configured to use it.
• Wrong proxy mode: V2rayN is set to "Direct" mode instead of "Global" or "Rule-based" proxy mode.
• TUN mode not activated: Some applications bypass the system proxy settings and need TUN (virtual network adapter) mode to be proxied.
• Antivirus/firewall blocking local proxy: Windows Defender or a third-party security tool is blocking V2rayN's local listener.

How to Fix It

Step 1: Check the proxy mode in V2rayN's bottom status bar. Click it to cycle through modes:

• Global: All traffic goes through the proxy (use this for testing)
• Rule-based: Only traffic matching rules goes through the proxy
• Direct: No traffic is proxied (this is your problem if you are in this mode)

Step 2: Verify the system proxy is set. Open Windows Settings, then Network and internet, then Proxy. You should see "Manual proxy setup" enabled with address 127.0.0.1 and port 10809 (or whatever port V2rayN uses).

Step 3: If applications still bypass the proxy, enable TUN mode in V2rayN:

1. Go to Settings, then TUN mode settings
2. Enable "TUN mode"
3. V2rayN will request administrator privileges to create the virtual network adapter
4. All system traffic (including apps that ignore system proxy settings) will now go through the tunnel

Step 4: Add V2rayN to your antivirus exceptions list. In Windows Defender: Virus and threat protection, then Manage settings, then Exclusions, then add the V2rayN installation folder.

Error: "Time Synchronization Error"

What This Error Means

VLESS Reality's handshake includes a timestamp validation step. If the client's system clock differs from the server's clock by more than approximately 90 seconds, the handshake is rejected. This is a security feature to prevent replay attacks.

What Causes It

• Wrong system time: The client's clock is set incorrectly (wrong timezone or drifted time).
• NTP disabled: The client's automatic time synchronization is turned off.
• Server time drift: The server's clock has drifted (less common on cloud VMs with NTP, more common on bare-metal servers).

How to Fix It

Windows:

# Open PowerShell as Administrator:
w32tm /resync
# Or: Settings then Time and language then Date and time then "Sync now"

Linux (server):

# Check current time:
timedatectl

# Enable NTP:
sudo timedatectl set-ntp true

# Force immediate sync:
sudo systemctl restart systemd-timesyncd
# Or if using chrony:
sudo chronyc makestep

Android: Settings, then System, then Date and time, then enable "Automatic date and time" and "Automatic time zone."

macOS:

# System Settings then General then Date and Time then "Set time and date automatically"
# Or from Terminal:
sudo sntp -sS time.apple.com

Verify both sides:

# On server:
date -u

# On client:
# Compare with https://time.is/ -- difference should be under 30 seconds

Skip VLESS Server Management Entirely

Every error on this page has one thing in common: they come from managing your own VLESS server. You need to configure xray-core, maintain certificates (for non-Reality setups), keep the server updated, monitor uptime, and debug cryptic error messages when something breaks.

There is a simpler approach: use a VLESS endpoint that is already configured, monitored, and running on real mobile carrier infrastructure.

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